Is the marriage considered valid if the father assumed guardianship of the new Muslim woman, and the contract was conducted in the presence of two Muslim witnesses via a group voice call on "WhatsApp," knowing that the witnesses' Islam was not verified, and the father was not the woman's legal guardian?

For a marriage (nikah (definition)) to be valid, the presence of the woman's guardian (wali) or his agent is a condition. The majority of scholars stipulate the testimony of two just Muslim men. However, the Maliki school permits delaying the testimony until before consummation (dukhūl). Some scholars also believe that public announcement (i‘lān) is sufficient for the validity of the marriage.

In the described situation, the testimony of two unknown men is insufficient. The solution is to have the marriage witnessed by two just witnesses, or to publicly announce the marriage, or to re-perform the marriage contract in the presence of the guardian and just witnesses, along with an announcement. A marriage contract performed via modern communication programs is valid, provided that the identities of the parties and the witnesses are verified.